<SEC-DOCUMENT>0001179110-20-000944.txt : 20200204
<SEC-HEADER>0001179110-20-000944.hdr.sgml : 20200204
<ACCEPTANCE-DATETIME>20200204114653
ACCESSION NUMBER:		0001179110-20-000944
CONFORMED SUBMISSION TYPE:	5
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20191231
FILED AS OF DATE:		20200204
DATE AS OF CHANGE:		20200204

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Lewis Holden
		CENTRAL INDEX KEY:			0001681628

	FILING VALUES:
		FORM TYPE:		5
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-16125
		FILM NUMBER:		20571285

	MAIL ADDRESS:	
		STREET 1:		6714 MELODY LANE
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20817

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FASTENAL CO
		CENTRAL INDEX KEY:			0000815556
		STANDARD INDUSTRIAL CLASSIFICATION:	RETAIL-BUILDING MATERIALS, HARDWARE, GARDEN SUPPLY [5200]
		IRS NUMBER:				410948415
		STATE OF INCORPORATION:			MN
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2001 THEURER BLVD
		CITY:			WINONA
		STATE:			MN
		ZIP:			55987
		BUSINESS PHONE:		5074545374

	MAIL ADDRESS:	
		STREET 1:		2001 THEURER BLVD
		CITY:			WINONA
		STATE:			MN
		ZIP:			55987
</SEC-HEADER>
<DOCUMENT>
<TYPE>5
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 5 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>5</documentType>

    <periodOfReport>2019-12-31</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <form3HoldingsReported>1</form3HoldingsReported>

    <form4TransactionsReported>0</form4TransactionsReported>

    <issuer>
        <issuerCik>0000815556</issuerCik>
        <issuerName>FASTENAL CO</issuerName>
        <issuerTradingSymbol>FAST</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001681628</rptOwnerCik>
            <rptOwnerName>Lewis Holden</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>603 5TH AVENUE SW</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>ROCHESTER</rptOwnerCity>
            <rptOwnerState>MN</rptOwnerState>
            <rptOwnerZipCode>55902</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer/EVP</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionCoding>
                <transactionFormType>3</transactionFormType>
                <footnoteId id="F1"/>
            </transactionCoding>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>7082</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">Pursuant to a dividend reinvestment program, the reporting person acquired 15 shares (30 shares post 2-for-1 split) on 8/18/2017, 13 shares (26 shares post 2-for-1 split) on 11/20/2017 and 13 shares (26 shares post 2-for-1 split) on 2/23/2018, which were not included in his last holdings report filed on 10/17/2018.</footnote>
        <footnote id="F2">The shares reported reflect a 2-for-1 stock split on May 22, 2019, in which the reporting person acquired an additional 3,500 shares.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ John J. Milek - Attorney-in-Fact</signatureName>
        <signatureDate>2020-02-04</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
